Title : Enhancing shellac stability using polyetheramines
Shellac is a unique natural resin derived from the secretion of insects, widely used as an enteric coating in the pharmaceutical industry. Despite the high potential of shellac as a protective coating and in controlled enteric drug delivery systems, its utilization is still limited due to its mechanical brittleness and poor stability caused by self-polymerization reactions. The study introduces a novel strategy for enhancing the stability of shellac through compounding with Jeffamine® polyetheramines. These biocompatible modifying agents combines two stabilization mechanisms: hydrophilic plasticizing and amine interaction with shellac carboxyl groups. The modified materials exhibited superior mechanical strength of up to one order of magnitude compared to native shellac. The new approach has demonstrated the preservation of solubility in ethanol during storage, as well as mechanical properties and thermal stability, over a period equivalent to 18 months at standard storage conditions. Based on Fourier Transform Infrared experiments, these beneficial effects were attributed to formation of amide bonds and acid-base interactions between shellac and Jeffamine®. Hence, the Jeffamine modification of shellac succeeds in hindering shellac self-polymerization occurring in native shellac and provides a significant improvement in the stability and shelf-life of shellac.